A federal judge presiding over the civil lawsuits stemming from the 1989 collapse of Charles H. Keating Jr.'s financial empire said that evidence so far tends to show that outside accountants and lawyers could be culpable for conspiring and aiding in fraudulent bond sales.

But U.S. District Court Judge Richard M. Bilby in Tucson, ruling on a procedural matter, was careful to point out that he was not determining the final outcome of the case.

Lawyers for small investors in Keating's company still have to prove the elements of fraud and racketeering at a trial scheduled for late next month, and defendants can contest the allegations to try to show there is no case, he said.

Bilby's opinion is important to thousands of small investors who lost more than $250 million nearly three years ago when Irvine-based Lincoln Savings & Loan failed and its parent company, American Continental Corp., went bankrupt.

The judge rejected defense motions to decertify the plaintiffs as a class with common allegations in each of more than a dozen class-action lawsuits. Had he granted the motions, the plaintiffs would have been forced to file individual lawsuits, an impossible situation for most of them.

More important, the opinion spurred some settlement talks, said Joseph W. Cotchett Jr. of Burlingame, one of the lawyers for bondholders.

"It's absolutely clear that the court is not going to be confused by a lot of legal technicalities," Cotchett said. "It's further clear that the bondholders are going to have their day in court and justice will be done."

If defendants are not trying to settle now, they "just weren't paying attention" to Bilby's decision, said Ronald Rus, an Orange lawyer who also represents bondholders.

Stuart L. Kadison, a Los Angeles lawyer for one of the major defendants, the Arthur Andersen & Co. accounting firm, said the strongly worded opinion probably will persuade some defendants to negotiate settlements.

But Arthur Andersen, which quit working for American Continental in October, 1986, before the bonds were sold, denies any wrongdoing and plans to go to trial, Kadison said.

Laurence M. Popofsky, a San Francisco lawyer for the Ernst & Young accounting firm, said the opinion merely sharpens the issues that the plaintiffs will have to prove at trial.

"The nature of the arguments before the court required the professional defendants to urge that there could be no class, even against Mr. Keating and other insiders," Popofsky said. "That was unacceptable to the court."

Keating, 68, was found guilty Dec. 4 on 17 counts of state securities fraud. He and four others were indicted a week later by a federal grand jury on fraud, conspiracy and racketeering charges. He is free on bail pending his sentencing in state court on Feb. 7.

Under Bilby's opinion, Popofsky said, the plaintiffs are going to have to prove, in effect, that the outside professionals conspired, aided or otherwise knew that a fraud was taking place.

Arthur Andersen, Ernst & Young, the accounting firm of Deloitte & Touche and the law firm of Jones, Day, Reavis & Pogue joined in the effort to decertify the plaintiffs' class.

They claimed that small investors relied on verbal sales presentations, not on the work of professionals. The presentations were varied, the defendants argued, and each of the purchasers relied on different pitches from American Continental representatives, who sold the bonds at Lincoln branches. Such reliance on different representations makes a trial on common allegations of misrepresentation impossible.

Bilby issued an oral denial of the motions on Dec. 31, but his 34-page written opinion just reached lawyers recently.

The alleged fraud "was not conceived or perpetrated by the bond representatives themselves," the judge said in his opinion. "Rather they were merely conduits of information communicated to them by or with the help of defendants."

He wrote that the evidence so far tended to support allegations that there was a "whole roster of deception designed to contrive a false image" of American Continental and Lincoln.

It "would be folly to force each bond purchaser to prove the nucleus of the alleged fraud again and again," he wrote.